1. Field of the Invention
This invention relates to electronic circuit devices.
2. Description of the Prior Art
Conventionally, electronic circuit devices are generally constituted with lines which connect elements such as transistors, capacitors, resistors, power supplies or the like, and A1 or the like is used for the material of the lines.
When a large current flows through lines of A1 or the like, the kinetic energy of the electrons is transferred to atoms or particles by collision of the electrons with the atoms or the particles, so a phenomenon generally called electromigration is said to occur in which the atoms or the particles move gradually with the flow of the electrons.
Therefore, the electromigration becomes apparent as current density in the lines increases. Especially if the movement of the atoms or the particles is not uniform (e.g., if there is a crystal grain boundary), the atoms or the particles decrease in some parts, and the parts of the lines would become small. In this case, more parts in the line become small, and the electric resistance in the lines as a whole would become high. In the worst case, the lines will be disconnected. Also, in the parts where the atoms or the particles gather, so called hillocks are liable to be formed, which is regarded to be a serious problem (i.e., a short circuit between the lines caused by the hillocks) especially in multilayer interconnection structure.
Because the life time of the lines with electromigration is regarded to be inversely proportional to the squar-cube of the current density, shrinkage of a line's sectional area by reduction in device size and increase in the current density thereby significantly decreases the life time of the lines.